title: Determinants of inapparent and symptomatic dengue infection in a prospective study of primary school children in Kamphaeng Phet, Thailand.
abstract: BACKGROUND
  Dengue viruses are a major cause of morbidity in tropical and subtropical regions of the world. Inapparent dengue is an important component of the overall burden of dengue infection. It provides a source of infection for mosquito transmission during the course of an epidemic, yet by definition is undetected by health care providers. Previous studies of inapparent or subclinical infection have reported varying ratios of symptomatic to inapparent dengue infection.
  
  
  RESULTS
  In a prospective study of school children in Northern Thailand, we describe the spatial and temporal variation of the symptomatic to inapparent (S:I) dengue illness ratio. Our findings indicate that there is a wide fluctuation in this ratio between and among schools in a given year and within schools over several dengue seasons. The most important determinants of this S:I ratio for a given school were the incidence of dengue infection in a given year and the incidence of infection in the preceding year. We found no association between the S:I ratio and age in our population.
  
  
  CONCLUSIONS
  Our findings point to an important aspect of virus-host interactions at either a population or individual level possibly due to an effect of heterotypic cross-reactive immunity to reduce dengue disease severity. These findings have important implications for future dengue vaccines.
authors.affiliation: Division of Infectious Disease, State University of New York, Upstate Medical University, Syracuse, New York, United States of America. endyt@upstate.edu
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Endy
authors.forename: Kathryn B
authors.initials: KB
authors.lastname: Anderson
authors.forename: Ananda
authors.initials: A
authors.lastname: Nisalak
authors.forename: In-Kyu
authors.initials: IK
authors.lastname: Yoon
authors.forename: Sharone
authors.initials: S
authors.lastname: Green
authors.forename: Alan L
authors.initials: AL
authors.lastname: Rothman
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Thomas
authors.forename: Richard G
authors.initials: RG
authors.lastname: Jarman
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Libraty
authors.forename: Robert V
authors.initials: RV
authors.lastname: Gibbons
mesh_terms: D000293:Adolescent; D058345:Asymptomatic Infections / Q000453:epidemiology; D002648:Child; D003715:Dengue / Q000453:epidemiology* / Q000473:pathology* / Q000821:virology; D003716:Dengue Virus / Q000302:isolation & purification*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D012574:Schools; D013334:Students; D013785:Thailand / Q000453:epidemiology